The Study On The Chromosome Genetic Relationship Between Different Ploidy Hybrids And Their Original Parents

The formation of tetraploid stock of the red crucian carps (Carassius auratus red var.,♀,2n=100) and common carps (Cyprinus carpio L.,(?),2n=100) provided an important platform for gaining the unique fish materials with different ploidy levels including diploids, triploids and tetraploids. Red crucian carp and common carp belong to different genera. The crossing between them is considered distal. The F2hybrids were derived from mating males with females of F1, and F3hybrids were produced by mating males with females of F2. The cytological analysis revealed that the females and males of F2hybrids were able to produce diploid eggs and diploid sperms that fertilized each other to form tetraploid fish in F3. In the allotetraploid population, both females and males were fertile.Crossing between RCC (♀) and BSB (?) generated two kinds of offspring, sterile triploid hybrids (3nRB,3n=124) and fertile tetraploid hybrids (4nRB,4n=148). The female4nRB hybrids were mature when they were two years old and could produce unreduced tetraploid eggs.4nRB (♀)×BSB (?) generated pentaploid hybrids5nRB (5n=172).In this study, we choose hybrid crucian carps at different ploidy levels, blunt snout bream and their parents as experiment materials. By breeding those fish, chromosome preparation, measured DNA content, amplified5SrDNA and a repeated sequence of263bp unit and the FISH technology to identify chromosome, we studied the number and structure of chromosome, the characters and the origin of chromosome and the homology of DNA sequence of these fish. The main results in this paper are presented as follows:1. By observation of kidney chromosome and karyotype analysis, we confirmed the number of chromosome, ploidy and the origin of chromosome of these hybrid fish.2. Comparison and analysis of5SrDNA and a repetitive element at centromere of different polyploid hybrids, the homology of the repeat sequence unit (263bp) in the chromosome centromere of hybrids and their parents is about93%-98%, indicated that these hybrids inherited stably the genetic information from their parents and they also obtained recombination and variation at some degree.3. Using the repeated sequence unit (263bp) at centromere as a probe of the specificity-red crucian carp for fluorescence in situ hybridization (FISH), the red crucian carp in hybrid crucian carp and blunt snout bream were all marked, so we precisely identify the origin of chromosomes of hybrid fish at the molecular cytogenetic level.